Method And System for Radio Access Technology Selection

ABSTRACT

A method and a multi-mode mobile communication device operating said method are provided. The method comprises a multi-mode mobile communication device selecting a first data connection carried over a first radio access technology (RAT) based on a first requested QoS, and the multi-mode mobile communication device selecting a second data connection over a second RAT based on a second requested QoS. The multi-mode communication device comprises a first transceiver adapted to be connected to a server using the first RAT, a second transceiver adapted to be connected to the server using the second RAT, and a processor for carrying out the method.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 13/170,552filed Jun. 28, 2011 which is also related to and claims priority fromU.S. Provisional Application Ser. No. 61/359,332, filed on Jun. 28,2010, entitled “Method and System for Operating a Multi-mode MobileCommunication Device”, the entire disclosure of which is herebyincorporated by reference for all purposes as if fully set forth herein.

The present patent disclosure relates generally to network and/or radioaccess technology (RAT) selection by a multi-mode mobile communicationdevice, and more specifically, to network and/or RAT selection by themulti-mode mobile communication device while in simultaneous coverage ofone or more networks using two or more RATs.

BACKGROUND

A multi-mode device that has performed association and registration withmultiple RAT networks, such as cellular and WLAN, can be addressed bythese networks independently. A typical implementation of a multi-modedevice will require the device to monitor all networks to which thedevice is registered for incoming data.

Different RATs may provide respective advantages when in communicationwith the multi-mode device. A cellular RAT may have a low wake-upfrequency in idle mode and a wide coverage area. A WLAN RAT may have ahigher wake-up frequency in idle mode and a limited coverage area, butmay provide higher data rates than cellular RATs and is preferred forapplications that benefit from a high data rate. From a powerconsumption perspective, cellular RATs are generally more efficient formulti-mode devices while in idle mode. However, WLAN RATs are generallymore efficient when transmitting at high data rates. In addition, userexperience during data activity is generally better over WLAN RATs.

A multi-mode mobile device in simultaneous coverage of two or more RATsmay not operate optimally. Each RAT may have one or more advantages overother RATs, such as power consumption, latency, data rate, coveragearea, tariffs, reliability, etc. There have been some efforts aimed toreduce power consumption of a multi-mode device by optimizing theinteraction between the multi-mode device and a network. For example, aPower-efficient Communication Protocol was proposed(http://www.antd.nist.gov/pubs/Slee-Power-Efficient-icc06.pdf) to turnoff the WLAN interface after a multi-mode device enters the idle state,and uses existing paging of a cellular RAT in order to wake up the WLANinterface. Unfortunately, this approach requires coordination betweenmultiple core network elements, including specific signaling and datatransfer between network elements, which is difficult and costly toimplement.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features of the patent disclosure will become moreapparent from the following description in which reference is made tothe appended drawings wherein:

FIG. 1 is an overview of a network in which an embodiment of the presentpatent disclosure may be implemented;

FIG. 2 depicts a multi-network wireless communication system in which anembodiment of the present patent disclosure may be implemented;

FIG. 3 is a flow chart showing an embodiment using the exemplarymulti-mode device in a system as illustrated in FIG. 2;

FIG. 4 illustrates the mobile originated data communication;

FIG. 5 illustrates the mobile terminated data communication;

FIG. 6 (a) illustrates an example of TIM periods;

FIG. 6 (b) illustrates an example of increase of TIM periods;

FIG. 6 (c) illustrates selective reception of the wake up signals;

FIG. 7 depicts an exemplary method of selecting a preferred dataconnection in accordance with one embodiment of the present patentdisclosure;

FIG. 8 depicts an exemplary method of selecting a preferred dataconnection in accordance with another embodiment of the present patentdisclosure; and

FIG. 9 shows a multi-mode device in accordance with an embodiment of thepresent patent disclosure.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In accordance with one aspect of the present patent disclosure there isprovided a network selection method comprising: a multi-mode mobilecommunication device selecting a first data connection carried over afirst radio access technology (RAT) based on a first requested QoS; andthe multi-mode mobile communication device selecting a second dataconnection over a second RAT based on a second requested QoS.

In one embodiment, the method further comprises: receiving anotification of a data transmission with the second requested QoSdestined for the multi-mode mobile communication device through thefirst data connection over the first RAT; and switching from the firstdata connection over the first RAT to the second data connection overthe second RAT.

In another embodiment, the method further comprises: upon receiving thenotification, establishing a first data call on the first RAT andcommencing the data transmission through the first data connection overthe first RAT; and establishing a second data call on the second RAT andactivating the second data connection over the second RAT; and switchingthe data transmission from the first data connection over the first RATto the second data connection over the second RAT; and receiving thedata transmission with the second requested QoS through the second dataconnection over the second RAT.

In another embodiment, the method further comprises: returning to thefirst data connection after a termination of the data transmission withthe second requested QoS; and awaiting notification of new datatransmission destined for the multi-mode mobile communication devicethrough the first data connection over the first RAT.

In another embodiment, the method further comprises: configuring aserver of data transmission destined for the multi-mode mobilecommunication device to use the first data connection while there is nodata to be transmitted, and the second data connection while there isdata is to be transmitted with the second requested QoS.

In another embodiment, the first RAT is a cellular radio accesstechnology, and the second RAT is a wireless local area network radioaccess technology.

In another embodiment, the first RAT is a wireless local area networkradio access technology, and the second RAT is a cellular radio accesstechnology.

In another embodiment, the first RAT is a first cellular radio accesstechnology, and the second RAT is a second cellular radio accesstechnology.

In another embodiment, the first RAT is a first wireless local areanetwork radio access technology, and the second RAT is a second wirelesslocal area network radio access technology.

In accordance with another aspect of the present patent disclosure thereis provided a method by a multi-mode mobile communication devicecomprising: selecting a first data connection based on a first criteriawhile there is no data to be transmitted, said first data connectioncarried over a first network utilizing a first radio access technology(RAT); selecting a second data connection based on a second criteriawhile data is being transmitted, said data connection carried over asecond network utilizing a second RAT; requesting a first QoS from awireless network or transport architecture while there is no data to betransmitted; and requesting a second QoS from a wireless network ortransport architecture while data is transmitted.

In accordance with another aspect of the present patent disclosure thereis provided a multi-mode mobile communication device comprising: a firsttransceiver adapted to be connected to a server using a first radioaccess technology (RAT); a second transceiver adapted to be connected tothe server using a second RAT; and a processor for selecting a firstdata connection carried over a first radio access technology (RAT) basedon a first requested QoS, and selecting a second data connection over asecond RAT based on a second requested QoS.

In accordance with another aspect of the present patent disclosure thereis provided a multi-mode mobile communication device comprising: a firsttransceiver adapted to be connected to a server using a first radioaccess technology (RAT); a second transceiver adapted to be connected tothe server using a second RAT; and a processor for selecting a firstdata connection based on a first criteria while there is no data to betransmitted, said first data connection carried over a first networkutilizing a first radio access technology (RAT), selecting a second dataconnection based on a second criteria while data is being transmitted,said data connection carried over a second network utilizing a secondRAT, requesting a first QoS from a wireless network or transportarchitecture while there is no data to be transmitted, and requesting asecond QoS from a wireless network or transport architecture while datais transmitted. The first and second networks are considered to bedifferent networks regardless of whether or not they are operated by thesame carrier. The first and second RATs may be the same or differentRATs.

Reference will now be made in detail to some specific embodiments of thepatent disclosure. Examples of these specific embodiments areillustrated in the accompanying drawings.

Multi-mode mobile communication devices, hereinafter generally referredto as multi-mode devices, have the capability to provide communicationservice on multiple radio access technologies (RATs) simultaneously orone at a time. The term “radio access technology” (RAT) in the presentdisclosure is intended to include any wireless technology which providesaccess to a network. Examples of RATs currently supported by amulti-mode device may include second generation (2G) wirelesscommunication systems such as Global System for Mobile communication(GSM), General Packet Radio Service (GPRS), Interim Standard 95 (IS-95);third generation (3G) systems such as CDMA2000 1x and 1xEV-DO, andUniversal Mobile Telecommunication System (UMTS) including High-SpeedPacket Access (HSPA) and evolved HSPA (HSPA+); fourth generation (4G)systems such as Long Term Evolution (LTE). In addition to these RATswhich operate on licensed spectrum and are typically known as cellularRATs, a multi-mode device may support different variants of IEEE802.x-based RATs such as WiFi and WiMAX, and provide Wireless Local AreaNetwork (WLAN) service on unlicensed spectrum. Furthermore, a multi-modedevice capable of supporting Unlicensed Mobile Access (UMA) can roam andhandover between cellular and WLAN RATs. The teachings of the presentdisclosure also apply to other examples of current generations of RATsand future generations of RATs.

Different technologies offer different benefits to end users. Forinstance, UMTS Wideband Code Division Multiple Access (WCDMA) cellularnetworks typically provide wide coverage area with data rates of up to384 kbps (release 99) or higher (e.g., evolved High-Speed Packet Access,HSPA+) while wireless local area networks can support very highconnection speeds (currently up to 600 Mbps) in a limited coverage area.Other examples of benefits to end users include lower tariffs, lowerlatency, higher reliability, etc., on different RATs. Networks operatedby the same carrier are considered to be different networks for thepurposes of this disclosure.

The term “multi-mode device” as used in the present disclosure includesany wireless mobile communication device which can use RATs of two ormore different RAT types. A single-mode device that can access two ormore instances of the same RAT type (e.g. two WCDMA networks) could alsobenefit from the teachings of the present disclosure.

The term “idle mode” as used in the present disclosure includes any modethat indicates an operation mode where no further data is expected to besent to or received from the multi-mode device for a prolonged period(e.g., “idle mode”, “power save mode”, “dormant mode”, “sleep mode”,“long discontinuous reception (DRX) mode”, “Cell_PCH state”, “URA_PCHstate”, etc.). One skilled in the art would appreciate that there may besignalling messages between the multi-mode device and the RAT during theidle mode, and that the mobile device “wakes up” periodically to monitorif there is data intended for the mobile device.

The term “active mode” as used in the present disclosure includes anymode that indicates an operation mode where data is being sent to orreceived from the multi-mode device (e.g., “active mode”, “connectedmode”, “continuous reception mode”, “short DRX mode”, etc.).

The term “data connection” as used in the present disclosure describesan end-to-end logical link between a multi-mode device and a networknode (for example, an e-mail server). The connection may require highdata rate for application such as video streaming or low data rate forapplications such as, e-mail or calendar synchronization.

The term “data transmission” is intended to describe a session where theactive data connection is transmitting packet data stream, or any otherforms of data stream. The term “data session” is synonymous.

The term “data call” is intended to describe a state where radio linkresources are assigned and active between the multi-mode device and thewireless network using the associated RAT. A data call can be eithermobile originated (MO) or mobile terminated (MT), meaning it isinitiated by the multi-mode device or the wireless network respectively.A data transmission requires an active data call in order to transmitpacket data.

The multi-mode device may support one or more simultaneous dataconnections, over one or more RATs. In each case, the data connectionprovides a logical address, for example but not limited to, an IPaddress, that allows data to be transferred between the multi-modedevice and other network nodes. The network nodes can use any one of theaddresses assigned to the multi-mode device in order to communicatedata, but will typically use just one, which is usually the address mostrecently used by the multi-mode device. The current patent disclosurecan apply to either type of network node, one that maintains multipleaddresses and data connections per multi-mode device, or one thatmaintains just a single address and data connection per device.

Each data connection is carried over a particular wireless network andits associated RAT, and can only be used while the multi-mode device isin the coverage area of the RAT. When in the coverage area of more thanone wireless network, the multi-mode device can use of any of severaldata connections to transfer data. The multi-mode device can also usedifferent data connections and RATs for different data services.Multi-mode devices will typically prefer the same data connection andRAT, regardless of whether the device and data connection are in activemode or idle mode.

Referring to FIG. 1, a multi-RAT communication environment 100, inaccordance with an embodiment of the present patent disclosure isillustrated. In this system, a multi-mode device 102 is able tocommunicate with multiple wireless network RATs such as wireless localarea network (WLAN) where an access point (AP) 110 is shown, and acellular UMTS/WCDMA network where a base station or node-B 106 is shown.Nodes 104 and 108 may be any other cellular network nodes, for examplebut not limited to, a base station of GSM/GPRS/EDGE and eNode-B of LTE.Further examples for different cellular systems may include otherwireless metropolitan or wide area networks (WMAN or WWAN), such asWiMAX and CDMAOne/CDMA2000, etc. As a non-limiting example, multi-modedevice 102 can communicate with GSM/EDGE 104, WCDMA 106, LTE 108, orWLAN 110. Thus, multi-mode device 102 may transmit voice or data signalsusing any of the supported RATs simultaneously. For uninterruptedservices, the multi-mode device 102 may be required to track thecommunication activities of a number of networks, the number may rangefrom 2, up to any practical number of supported modes.

A multi-mode device when in the coverage area of multiple networks withmultiple RATs, may not communicate efficiently and optimally. Forexample, from a power consumption point of view, it is costly for amulti-mode device to continuously monitor the status and data activityof multiple data connections.

As used in this patent disclosure, where the optimization criteria isthe non-limiting example of power saving, the first network and RATgenerally has a low wake-up frequency in idle mode, wide coverage area,lower throughput and is suitable for low data rate and idle modeoperations; the second network and RAT has higher wake-up frequency inidle mode, limited coverage area, higher throughput and is suitable forhigh data rate operations. The present patent disclosure would alsoapply even if both networks share the same RAT type, provided theoptimization criteria would select the first network for idle mode andthe second network for active mode, based on the network RAT settingsand coverage. In this case, a single-mode device could also benefit fromthe current invention.

For illustrative purposes and as a non-limiting example, the multi-modedevice 102 may support WLAN and WCDMA technologies and it is in thecoverage area of access point (WLAN) 110 and Node-B (WCDMA) 106. Whilein idle mode, the multi-mode device 102 must wake up periodically tomonitor for downlink data activity in both RATs independently. For theexemplary WCDMA network, this is achieved through periodic monitoring ofpaging indicator channel (PICH), where the multi-mode device wakes upits receiver and decodes PICH message to see if there is a call, packetor voice call for itself. This is also called discontinuous reception(DRX), where the device turns off its radio between paging cycles toreduce battery consumption. A typical paging cycle configuration forWCDMA networks is 1.28 seconds, compared with a typical wake-up cycle of100 milliseconds for WLAN. Monitoring WLAN in addition would decreasebattery life compared with monitoring WCDMA alone.

Referring to FIG. 2, an exemplary network infrastructure 200 in whichthe embodiments of the present patent disclosure may be illustrated. Ascan be seen, a multi-mode device 102 that is registered (i.e.,associated/attached/etc.) to both WLAN/WCDMA networks can obtain networkIP addresses and be addressed by either network through either a firstor a second IP address. A first data connection 204 with itscorresponding first IP address is established over a WCDMA network 206using a PDP context activation procedure, and a second data connection210 with its corresponding second IP address is established over a WLANnetwork access point 212 using a Dynamic Host Configuration Protocol(DHCP). Both data connections provide an interface to the IP basednetwork 216 and the data server 214. The server 214 is illustrated as asingle server in FIG. 2, it should be apparent to a person skilled inthe art that multiple servers may also be used.

In accordance with one embodiment of the present patent disclosure, themulti-mode device 102, connected through a plurality of RATs to theserver 214, and after considering one or more criteria, may choose afirst data connection 204 over a first RAT, to monitor the data activityin idle mode and/or low data rate applications. For example, themulti-mode device may select a WCDMA network and RAT with a longerDiscontinuous Reception (DRX) cycle and/or lower overhead technology fordownlink paging (wake-up cycle), but then switch to a WLAN network andRAT that supplies high data rates for applications like video streaming,ftp download, etc., when needed. More generally, a first RAT isprioritized over a second RAT after considering a first optimizationcriteria, for example but not limited to, power saving, tariff, callset-up latency, concurrency with other services, and a QoS requirement.The arrival of data at the multi-mode device is monitored on the firstRAT in the idle mode. When a data connection is active, a secondoptimization criteria (for example but not limited to, data throughputrequirement, power saving, tariff, data packet latency, data packetjitter, concurrency with other services, a QoS requirement and bandwidthoptimization) may be considered. The second RAT may then be selectedover the first RAT for the ongoing data session.

The server 214 and the multi-mode device 102 may share a common protocolto communicate with each other for selecting a preferred dataconnection. This would be the case for servers that support more thanone data connection simultaneously per multi-mode device. Such aprotocol allows the multi-mode device 102 to request a preferred RAT foruse in communications, based on an optimization criteria, for a givendata activity or idle mode operation. Other servers may only support onedata connection at a time and typically this data connection is the onemost recently used by the multi-mode device.

This is in stark contrast to typical operation of a multi-mode devicewithout the present invention. In this case, a multi-mode device woulduse all of its data connections whether or not there are ongoing datatransmissions, and would need to monitor all of its data connectionsduring idle mode for incoming, i.e. mobile terminated (MT) data calls.Specifically, if a multi-mode device activates a data connection on aparticular network and RAT, it will continue to monitor this dataconnection for incoming calls during any idle mode periods on saidnetwork and RAT, even if another network and RAT is currently preferredfor data transmissions.

FIG. 3 is a flow chart showing an embodiment of the present patentdisclosure using the exemplary multi-mode device 102 in a network 200 asillustrated in FIG. 2. The multi-mode device 102 turns on WLAN and WCDMAinterfaces sequentially. After turning on WLAN interface, the multi-modedevice 102 associates 302 with the access point 212, obtains an IPaddress if necessary (e.g. DHCP), and activates 304 the second dataconnection 210 between the server 214 and the multi-mode device 102.After turning on the WCDMA interface, the multi-mode device 102 attaches306 with the Node B 208 and activates 308 the first data connection 204between the server 214 and multi-mode device 102. It should be apparentto a person skilled in the art that the WCDMA and WLAN interfaces couldbe activated in either order, or even simultaneously, and that FIG. 3simply describes one such possibility.

Referring to FIG. 2 and FIG. 3, after considering the first criteria,for example, a possible battery saving, the multi-mode device 102 in theidle mode may prefer and prioritize 310 the first data connection 204and requests that the server 214 use the first data connection 204through the WCDMA network. Therefore, the multi-mode device 102 removesthe requirement to monitor network activities on the battery intensiveWLAN network in idle mode, as no data is expected to arrive over thesecond data connection 210 over the WLAN network. The multi-mode device102 may completely power down the WLAN radio, or otherwise reduce thefrequency of monitoring. The multi-mode device 102 may or may nottrigger a disassociation process with the WLAN network.

When a data transmission is initiated by the server 214, the currentlypreferred data connection 204 using the WCDMA network 206 is used tobegin the transmission. If the multi-mode device 102 then prioritizesthe second data connection 210 based on a second optimization criteria(e.g. higher data rate, shorter transfer time, lower energy pertransfer, lower tariff, etc.), it will switch to the second dataconnection 210 over the second network 212, e.g. WLAN RAT. This willinvolve activating the WLAN radio of the multi-mode device 102, andpossibly re-associating and reactivating the data connection 210,depending on the current state of the connection. The server 214 willalso switch to the second data connection 210 after receiving the firstdata packet over this data connection. The multi-mode device 102 mayoptionally use an explicit signaling protocol over one or both dataconnections to inform the server 214 about the switch, and/or suspendand resume the data transmission during the switchover.

Referring to FIG. 4 and FIG. 5, a data transmission between themulti-mode device 102 and the server 214 can be either mobile originatedon the uplink 402, 404 or mobile terminated on the downlink 406, 408.The behavior for these two examples differs. The difference in behavioris due to the fact that the server 214 located in the network canmonitor traffic activity constantly on either of the data connections204, 210 (i.e. IP addresses IP:1 and IP:2).

Referring to FIG. 4, if the data transmission is mobile originated 402,404, then the multi-mode device 102 can choose which data connection tosend the data on, based on the second optimization criteria (e.g. higherdata rate, shorter transfer time, lower energy per transfer, lowertariff, etc.). If the multi-mode device 102 selects the first dataconnection 204 over the first network, for example, WCDMA RAT 206, thenthe device initiates the data transmission using the first dataconnection 402. Once the data transmission is complete, the multi-modedevice 102 reverts to idle mode and continues to prioritize the firstdata connection based on the first optimization criteria.

If, after considering the second criteria, the multi-mode device 102selects the second network, e.g. WLAN RAT 212, then the device canimmediately initiate the data transmission over the second dataconnection 404. This will involve activating the WLAN radio of themulti-mode device 102, and possibly re-associating and reactivating thedata connection 210, depending on the current state of the connection.Once the data transmission is complete, the multi-mode device 102reverts to idle mode, but first switches back to the first dataconnection 204 (i.e. WCDMA RAT 206) based on the first optimizationcriteria, and requests that the server 214 also use the first dataconnection for any future mobile terminated data transmissions.

Referring to FIG. 5, if the data transmission is mobile terminated, thenthe server will use the first data connection 204 to initiate the datatransmission over the first RAT 406, as this is the RAT the multi-modedevice 102 is using to monitor for incoming data while in idle mode.After the data call is established on the first RAT, the multi-modedevice 102 will select a data connection and RAT for the (remaining)data transmission, based on a second optimization criteria. If thedecision is to continue to use the first RAT 406, then the alreadyestablished data call continues until the transmission ends, and thedevice reverts to idle mode using the first data connection.

If the multi-mode device 102 selects the second RAT after consideringthe second criteria, it will switch to the second data connection 210over the second network, e.g. WLAN RAT 212. This will involve activatingthe WLAN radio of the multi-mode device 102, and possibly re-associatingand reactivating the data connection 210, depending on the current stateof the connection. The server 214 will also switch to the second dataconnection 210 after receiving the first data packet from the multi-modedevice 102 over this data connection. The multi-mode device 102 mayoptionally use an explicit signaling protocol over one or both dataconnections to inform the server 214 about the switch, and/or suspendand resume the data transmission during the switchover.

In accordance with one embodiment of the present invention, a multi-modedevice in the coverage area of multiple networks, based on a firstoptimization criteria, will monitor a single preferred network and RATin order to receive incoming data transmissions. With no requirement tomonitor the other networks, the multi-mode device can reduce oreliminate network monitoring activities and thereby improve batterylife. The multi-mode device can power down all radios associated withthe unused networks and RATs. The multi-mode device can alternatelyreduce the frequency of monitoring unused networks, decreasing theamount of radio activity while in the idle state. The frequency canoptionally be chosen to minimize the likelihood of becoming unknown(e.g. deregistered, disassociated, unattached, disconnected, etc.) inthe network, based on the protocols of the associated RATs. Remainingknown in a network has the benefit of reducing the latency in startingdata calls and initiating/transitioning data transmissions in thisnetwork and RAT. The multi-mode device can alternately explicitly removeitself from the unused networks by following the appropriate procedures(e.g. deregister, disassociate, detach, disconnect, etc.) of theassociated RATs.

Using the exemplary embodiments of WCDMA as the first network RAT andWLAN as the second network RAT as illustrated in FIG. 2 and FIG. 3, andpower saving as the first optimization criteria, the multi-mode device102 may also avoid monitoring paging notifications relayed on beaconmessages of associated access point 212 by two different approaches: i)by renegotiating 312 the wake-up cycle with the access point 212 as willbe described below; and ii) ignoring a subset of beacon messages, andlowering the frequency of messages that are monitored/received to theminimum level required to avoid disassociation with the access point.The second approach also saves the multi-mode device 102 additionalre-association process. The second approach is possible as themulti-mode device 102 does not expect any packet from WLAN network aftersteering data connection on to WCDMA network.

Referring to FIG. 2 and FIG. 6 (a), the access point 212 of the secondRAT and the multi-mode device 102 exchange management signals. Themanagement signals from the access point 212 may include a value forbroadcast transmission interval 604, for example, a beacon interval inWLAN, representing the amount of time between beacon transmissions.Before the multi-mode device 102 enters idle mode as described below,multi-mode device 102 needs the transmission interval to know when towake up to receive the beacon message, and learn whether there arebuffered frames at the access point 212 for itself. The managementsignals from the access point 212 may further include a timestamp. Afterreceiving a management signal, for example a beacon frame, themulti-mode device 102 uses the timestamp value to update its localclock. This process enables synchronization among all multi-mode mobilecommunication devices that are associated with the same access point.The management signals may further include, for example, in WLAN, aService Set Identifier (SSID) for identifying a specific WLAN.

The multi-mode device 102 associates with the access point 212 to gainfull access to the network, by sending an Association Request. TheAssociation Request carries information about the multi-mode device 102,for example but not limited to, supported data rates, and the SSID ofthe network it wishes to associate with.

The access point 212 processes the Association Request. The access point212 grants association and responds with an Association Responseincluding a successful status code, and the Association ID to identifythe station for delivery of buffered frames when in idle mode.

The multi-mode device 102 in idle mode monitors beacon frames forindications concerning data buffered at the access point 212. In WLAN,this is determined by a Traffic Indication Message period value whichspecifies how often a beacon frame includes a Traffic Indication Messagefor a considered multi-mode device, and this number is included in eachbeacon frame as part of the Traffic Indicator Map (TIM). For example,referring to FIG. 6 (a), each beacon frame 602 may include a TIM periodof 5 and every fifth beacon frame 602, as indicated by arrows 606, mayinclude a TIM including the considered multi-mode device. TIM identifiesclient devices for which unicast (dedicated) traffic is pending andbuffered in the access point 212, and includes an indication whetherbroadcast or multicast traffic is pending.

Upon entering idle mode, the multi-mode device 102 may transmit anotification to the access point 212, so that the access point 212 willknow how to handle unicast traffic destined for the multi-mode device102. The multi-mode device 102 will begin to sleep according to the TIMperiod, as explained above.

FIG. 6 (b) illustrates the increase of the TIM period from 5, asindicated by 606 in FIGS. 6 (a) to 35, as indicated by 608, after anassociation or re-association request with an increased “ListenInterval” is received at the access point 212. It should be conceivablethat the TIM may be increased to infinite, thereby setting themulti-mode device 102 to terminate the communication on the WLAN.

Alternatively, and referring to FIG. 6 (c), the beacon interval 604 mayremain the same, but the multi-mode device 102 ignores some beaconmessages and listens beacon messages 610 with an alternate frequency.

The need for power saving in a battery-powered multi-mode device 102 mayincrease over time as the battery drains, therefore, the receiveinterval of the management signal may be tuned based on the batterylevel of the multi-mode device 102. More generally, as apparent to aperson skilled in the art, the receive interval of the management signalmay be tuned according to a plurality of internal or external factors,such as the usages of the first wireless communication mode and secondwireless communication mode in the network 100, the cost of datatransfer in the first wireless communication mode and second wirelesscommunication mode, type of data connection/application, data rate,connection condition etc.

Referring to FIG. 7, the method of selecting a preferred data connectionafter considering an optimization criteria, for example, but not limitedto, power saving, communication type, data rate and idle mode operationis illustrated. The method selects between multiple networks,specifically a first and second network for operation in the idle andactive modes respectively, based on the characteristics andconfigurations of their associated RATs. This includes the case of bothfirst and second RATs being of the same type, e.g. WCDMA, if theircharacteristics and/or configurations would result in differentselection decisions by the multi-mode device.

In FIG. 7, the first RAT has first characteristics for selection basedon a first criteria, for example but not limited to: power saving,tariff, call set-up latency, concurrency with other services, a QoSrequirement, a low wake-up frequency, wide coverage area, and lowerthroughput and is suitable for low data rate and idle mode operations.An example of the first RAT may be, but is not limited to WCDMA. Thesecond RAT has second characteristics for selection based on a secondcriteria, for example but not limited to: data throughput, data transfertime, power saving, tariff, data packet latency and jitter, concurrencywith other services, a QoS requirement, higher wake-up frequency,limited coverage area, higher throughput and is suitable for high datarate operations. An example of the second RAT may be, but is not limitedto WLAN. In this example, the first WCDMA RAT is preferable to thesecond WLAN RAT for idle mode operations, when considering a particularoptimization criteria, for example, long battery life.

The multi-mode device is assumed to be in the coverage of multiplewireless networks and their associated RATs, at least a first RAT and asecond RAT. Upon detecting both RATs, the multi-mode device may connect(e.g. associate, attach, register, etc.) to both RATs. The multi-modedevice is in an idle state 702, i.e. no significant data is beingtransmitted, although network and RAT specific signaling messages may beexchanged between the network and the multi-mode device 102 from time totime.

A first RAT is prioritized based on a first criteria 704, for examplebut not limited to: power saving, tariff, call set-up latency,concurrency with other services, and a QoS requirement. A first dataconnection is then established over the first RAT 706. The multi-modedevice monitors for the arrival of data 708 using the first dataconnection over the first RAT. The first RAT indicates (e.g. signals,page, etc.) the arrival of pending downlink data 710 for the multi-modedevice, and sets up a first data call for the pending data transmission712. However, after considering the second optimization criteria 714, asecond data call and data connection may be established over the secondRAT 716. The data transmission is then switched from the first dataconnection to the second data connection 718. When the data transmissionterminates, the multi-mode device returns to the first data connectionover the first RAT 720.

FIG. 8 illustrates another embodiment of the present patent disclosure.In this non-limiting example, in the presence of two networks and RATs,for example, a first WCDMA network and a second WLAN network, amulti-mode device 102 associates and attaches to both RATs, in order tobe properly addressed and located in both wireless networks. A firstdata connection over the first RAT and a second data connection over thesecond RAT are established 802 between the server 214 and the multi-modedevice 102. Unless there is an immediate data activity the devicetypically goes to idle mode in both RATs. In the example of WLAN andWCDMA, considering the lower DRX and corresponding battery saving, thedevice may choose to prioritize and select the first RAT, in thisexample, WCDMA, for idle mode operation. Based on a first criteria, thefirst data connection over the first RAT is selected 804 to monitor forany upcoming data transmissions 808 and the server is configuredaccordingly 806. When a data needs to be transmitted between the mobiledevice and the server 810, a second optimization criteria may beconsidered 812. If the second data connection over second RAT is chosen,there are two scenarios: for mobile originated data transmission, themulti-mode device initiates the data transmission using the second dataconnection over the second RAT 814; for mobile terminated datatransmission, the data transmission may initially take place over theoriginal first data connection over the first RAT 816, and then switchto the second data connection over the second RAT 818. When the datatransmission is terminated, the monitoring of the arrival of datareturns to the first data connection 820.

In the above example, the multi-mode device performs an evaluation toselect the operational RAT for idle mode based on the first criteriasuch as power saving for the mobile device. It should be apparent to aperson skilled in the art that many optimization criteria may be used toselect the first RAT for idle mode operation, and similarly (either sameor different criteria) select the second RAT for active mode operation.Example criteria include, but are not limited to, power saving, coveragearea, reliability, tariff, connection type, application type triggeringthe data connection, call set-up latency, data rate requirement, datatransfer time, concurrency with other services, connection condition,QoS requirement etc.

For example, the call set-up requirement of the main application of thedevice may decide the preferred operational RAT for idle mode. Forexample, Push To Talk (PTT) typically requires very low latency insetting up calls. If PTT is the primary application on a multi-modedevice, the multi-mode device may choose not to utilize the proposedbattery-saving algorithm, but rather select the RAT with a shorter DRXas PTT requires very short call set-up times. In yet another embodiment,the tariff for the service may dictate which connection and RAT to use,for example, the prioritized first RAT may provide less expensive oreven free services (e.g. free incoming calls) compared with the secondRAT.

In yet further embodiments, the state of the first RAT and the secondRAT may be considered as one of the optimization criteria; or theconcurrency of other services with the current service. An ongoing datatransmission or voice call on either RAT would optionally prioritizethat RAT for any other services, removing the need to monitor the otherRAT for the duration of the ongoing voice or data call. For the exampleof WCDMA and WLAN, an ongoing PTT voice call on the second WLAN RAT maytrigger a decision by the multi-mode device to temporarily shift allother data services to the second data connection from the previouslyprioritized first data connection, removing the need to monitor thefirst WCDMA RAT for incoming data calls.

The examples presented above also focused on packet switched connectionwhere there is no interaction or presence of other connection types likecircuit switched calls, for example, voice or video telephony calls, orPTT type of connections. Different combinations of these scenarios maybe evaluated by the multi-mode device. The multi-mode device may alsoselect the active mode RAT and data connection based on the optimalbattery usage. As an example, if there is an ongoing circuit-switchedvoice connection on the first RAT, then the multi-mode device mightdecide to also use the first RAT for packet connectivity at the sametime, utilizing the already active and operational transceiver forpacket data communications. In this scenario, using the second RAT forpacket data communications would engage an additional transceiver forWLAN, draining the battery faster.

Furthermore, there may be a plurality of criteria being considered whenprioritizing the data connections, for example, a first criteria beingconsidered may be power saving, and a second criteria being consideredmay be a data rate in the data connections.

In general, the mobile device evaluates a plurality of RAT and availabledata connections, and decides the preferred operational RAT afterconsidering one or more optimization criteria, and inform the server totransmit the data on the preferred operational connection.

The present patent disclosure is also applicable to more sophisticatednetwork or transport architectures that are themselves capable ofsupporting and switching between a plurality of RATs. The network ortransport architecture may be implemented in the network, the mobiledevice, or both. Such a network architecture may implement a transportlayer or other mechanism that would determine the preferred operationalRAT, for example selecting between different RAT for differentapplication services with different data transmission requirements.Typically, these networks optimize RAT selection for the available andsubscribed application services, but do not usually differentiatebetween an active and an idle service.

A multi-mode mobile device operating in such a network may indicatedifferent data transmission requirements for the same available servicedepending on whether that service is currently active. The differentdata transmission requirements may in turn cause the network ortransport architecture to select different RATs. For example, themulti-mode mobile device may indicate a low minimum requirement for aparticular service while there is no active data transmission, and bedirected by the network or transport architecture to a first RAT tomonitor for upcoming data transmissions. Upon activating a datatransmission in either direction, the multi-mode mobile device canindicate a higher minimum requirement for the now active service, and bedirected by the network or transport architecture to a second RAT tocontinue the data transmission.

It should be apparent to one skilled in the art that a multi-mode mobiledevice supporting and operating in such a network can still influenceand determine the selection of a RAT by judicious choice of theindications and inputs to the network or transport architecturemechanism controlling RAT selection. One embodiment of the presentpatent disclosure may select a first RAT while there is no data to betransmitted by selecting a first set of indications and inputs, andselect a second RAT during an active data transmission by selecting asecond set of indications and inputs.

In a non-limiting example, the multi-mode mobile device could indicate avery low data throughput requirement while there is no data to betransmitted, and be directed to select a first RAT, for example but notlimited to, a WCDMA network with lower DRX cycle to monitor for upcomingdata transmissions. During an active data transmission, the multi-modemobile device could update the minimum data throughput requirement to ahigher value, and be directed to switch to a second RAT, for example butnot limited to, a WLAN network with higher data rates.

In general, the multi-mode mobile device could indicate one or morecriteria, for example, but not limited to, minimum data rate, data rate,call setup latency, data latency, jitter, guaranteed delivery,reliability, tariff, power saving, or other QoS requirement.

Referring now to FIG. 9, in accordance with an embodiment of the presentpatent disclosure, a multi-mode device 102 is shown. The multi-modedevice 102 may be a portable or a mobile telephone, a Personal DigitalAssistant (PDA), a wireless video or multimedia device, a portablecomputer, an embedded communication processor or other wirelesscommunication device.

The multi-mode device 102 comprises a processor 902 for carrying outoperational processing for the multi-mode device 102. The multi-modedevice 102 also has a first transceiver 904 for providing wirelesscommunication via a first RAT, for example but not limited to, WCDMA;and a second transceiver 906 for providing wireless communication via asecond RAT, for example but not limited to, WLAN. The present inventionmay also be generalized to any multi-mode device 102 that supports morethan two transceivers and/or RATs.

Each of the transceivers 904 and 906 typically includes an antenna 908,910, a modulation/demodulation section (not shown), and acoding/decoding section (not shown), for example, as will be known to askilled person and thus will not be described further herein. Thetransceiver 904 and 906 are coupled to the processor 902.

The processor 902 may be a single processor or may comprise two or moreprocessors carrying out all processing required for the operation of themulti-mode device 102. The number of processors and the allocation ofprocessing functions to the processing unit is a matter of design choicefor a skilled person. The multi-mode device 102 also has a programmemory 912 in which programs containing processor instructions foroperation of the multi-mode device 102 are stored. Specific programelements stored in program memory 912 may include a selector forselecting operational RAT. The multi-mode device 102 further includes aoptimizer for considering the optimization criteria.

The selector receives indications that both transceivers 904 and 906 arereceiving and transmitting signals in their respective RAT. For example,the second transceiver 906 receives and transmits a WLAN signal whilethe first transceiver 904 receives and transmits a WCDMA signal. Themulti-mode device 102 determines that with no active data transmission,the second transceiver 906 in idle mode consumes more battery power thanthe first transceiver 904. Accordingly, the multi-mode device 102 cancommunicate with the IP server in the network (e.g. e-mail server) toprioritize the data connection provided by the first transceiver 904.The multi-mode device 102 may deactivate and power down the secondtransceiver 906, and may also optionally indicate this via explicitsignaling to the network and RAT provided by the second transceiver 906.In another embodiment, the multi-mode device may optionally re-negotiatewith the wireless network and RAT provided by the second transceiver 906to increase the DRX period. In the exemplary WLAN, the request may be inthe form of a Listen Interval in the Association or Re-associationrequest or through any other method for other RATs. After receivingAssociation or Re-association response from the WLAN network, theselector monitors the management signal (beacon frame) via the secondtransceiver 906 at increased time intervals. At the same time, theselector monitors the first transceiver 904 for incoming datatransmissions. This may include using a low overhead technology (e.g.WCDMA) for downlink paging. Once an active data transmission is inprogress, the selector may select the first transceiver 904 forcommunicating data, for example, preferring to use transceiver 904 forlow data rate applications, or the selector may switch to the secondtransceiver 906, for example, preferring to use transceiver 906 for highdata rate applications such as video streaming, ftp download, etc.

Further, although two separate transceivers 904 and 906 are illustratedin FIG. 9. It should be apparent to a person skilled in the art that asingle transceiver with a single interface may also provide more thanone RAT.

While the patent disclosure is described in conjunction with thespecific embodiments, it will be understood that it is not intended tolimit the patent disclosure to the described embodiments. On thecontrary, it is intended to cover alternatives, modifications, andequivalents as may be included within the scope of the patent disclosureas defined by the appended claims. In the above description, numerousspecific details are set forth in order to provide a thoroughunderstanding of the present patent disclosure. The present patentdisclosure may be practiced without some or all of these specificdetails. In other instances, well-known process operations have not beendescribed in detail in order not to unnecessarily obscure the presentpatent disclosure.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the patentdisclosure. As used herein, the singular forms “a”, “an” and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise. It will be further understood that the terms“comprises” or “comprising”, or both when used in this specification,specify the presence of stated features, integers, steps, operations,elements, and/or components, but do not preclude the presence oraddition of one or more other features, integers, steps, operations,elements, components, and/or groups thereof.

It is further understood that the use of relational terms such as firstand second, and the like, if any, are used solely to distinguish onefrom another entity, item, or action without necessarily requiring orimplying any actual such relationship or order between such entities,items or actions.

The flowchart and block diagrams in the figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods and computer program products according to variousembodiments of the present patent disclosure. In this regard, each blockin the flowchart or block diagrams may represent a module, segment, orportion of code, which comprises one or more executable instructions forimplementing the specified logical function (s). It should also be notedthat, in some alternative implementations, the functions noted in theblock may occur out of the order noted in the figures. For example, twoblocks shown in succession may, in fact, be executed substantiallyconcurrently, or the blocks may sometimes be executed in the reverseorder, depending upon the functionality involved. It will also be notedthat each block of the block diagrams and/or flowchart illustration, andcombinations of blocks in the block diagrams and/or flowchartillustration, can be implemented by special purpose hardware-basedsystems that perform the specified functions or acts, or combinations ofspecial purpose hardware and computer instructions.

Some portions of the detailed description in the above are presented interms of algorithms and symbolic representations of operations on databits or binary digital signals within a computer memory. Thesealgorithmic descriptions and representations may be the techniques usedby those skilled in the data processing arts to convey the substance oftheir work to others skilled in the art.

An algorithm is generally, considered to be a self-consistent sequenceof acts or operations leading to a desired result. These includephysical manipulations of physical quantities. Usually, though notnecessarily, these quantities take the form of electrical or magneticsignals capable of being stored, transferred, combined, compared, andotherwise manipulated. It has proven convenient at times, principallyfor reasons of common usage, to refer to these signals as bits, values,elements, symbols, characters, terms, numbers or the like. It should beunderstood, however, that all of these and similar terms are to beassociated with the appropriate physical quantities and are merelyconvenient labels applied to these quantities.

Unless specifically stated otherwise, as apparent from the abovediscussions, it is appreciated that throughout the specificationdiscussions utilizing terms such as “processing,” “computing,”“calculating,” “determining,” or the like, refer to the action and/orprocesses of a computer or computing system, or similar electroniccomputing device, that manipulate and/or transform data represented asphysical, such as electronic, quantities within the computing system'sregisters and/or memories into other data similarly represented asphysical quantities within the computing system's memories, registers orother such information storage, transmit session or display devices.

Embodiments within the scope of the present patent disclosure can beimplemented in digital electronic circuitry, or in computer hardware,firmware, software, or in combinations thereof. Apparatus within thescope of the present patent disclosure can be implemented in a computerprogram product tangibly embodied in a machine-readable storage mediumfor execution by a programmable processor; and method actions within thescope of the present patent disclosure can be performed by aprogrammable processor executing a program of instructions to performfunctions of the patent disclosure by operating on input data andgenerating output. Embodiments within the scope of the present patentdisclosure may be implemented advantageously in one or more computerprograms that are executable on a programmable system including at leastone programmable processor coupled to receive data and instructionsfrom, and to transmit data and instructions to, a data storage system,at least one input device, and at least one output device. Each computerprogram can be implemented in a high-level procedural or object orientedprogramming language, or in assembly or machine language if desired; andin any case, the language can be a compiled or interpreted language.Suitable processors include, by way of example, both general and specialpurpose microprocessors. Generally, a processor will receiveinstructions and data from a read-only memory and/or a random accessmemory. Generally, a computer will include one or more mass storagedevices for storing data files. Embodiments within the scope of thepresent patent disclosure include computer-readable media for carryingor having computer-executable instructions, computer-readableinstructions, or data structures stored thereon. Such computer-readablemedia may be any available media, which is accessible by ageneral-purpose or special-purpose computer system. Examples ofcomputer-readable media may include physical storage media such as RAM,ROM, EPROM, CD-ROM or other optical disk storage, magnetic disk storageor other magnetic storage devices, or any other media which can be usedto carry or store desired program code means in the form ofcomputer-executable instructions, computer-readable instructions, ordata structures and which may be accessed by a general-purpose orspecial-purpose computer system. Any of the foregoing can besupplemented by, or incorporated in, ASICs (application-specificintegrated circuits). It should be understood that embodiments of thepresent patent disclosure may be used in a variety of applications.Although the present patent disclosure is not limited in this respect,the methods disclosed herein may be used in many apparatuses such as inthe transmitters, receivers and transceivers of a radio system. Radiosystems intended to be included within the scope of the present patentdisclosure include, by way of example only, cellular radiotelephonecommunication systems, satellite communication systems, two-way radiocommunication systems, one-way pagers, two-way pagers, personalcommunication systems (PCS), personal digital assistants (PDA's),notebook computers in wireless local area networks (WLAN), wirelessmetropolitan area networks (WMAN), wireless wide area networks (WWAN),or wireless personal area networks (WPAN, and the like).

What is claimed:
 1. A method comprising: selecting a first active dataconnection by a multi-mode mobile communication device while there is nodata to be transmitted, said first active data connection carried over afirst network utilizing a first radio access technology (RAT) based on afirst criteria; receiving a notification of a data transmission destinedfor the multi-mode mobile communication device through the first dataconnection over the first RAT; selecting a second active data connectionby the multi-mode mobile communication device while data is beingtransmitted, said second active data connection carried over a secondnetwork utilizing a second RAT based on a second criteria; and switchingfrom the first active data connection over the first RAT to the secondactive data connection over the second RAT.
 2. The method according toclaim 1, further comprising: upon receiving the notification,establishing a first data call on the first RAT and commencing the datatransmission through the first active data connection over the firstRAT; establishing a second data call on the second RAT and activatingthe second active data connection over the second RAT; switching thedata transmission from the first active data connection over the firstRAT to the second active data connection over the second RAT; andreceiving the data transmission through the second active dataconnection over the second RAT.
 3. The method according to claim 1,further comprising: returning to the first active data connection aftera termination of the data transmission; and awaiting notification of newdata transmission destined for the multi-mode mobile communicationdevice through the first active data connection over the first RAT. 4.The method according to claim 2, wherein after a termination of the datatransmission, further comprising: returning to the first active dataconnection over the first RAT; closing the second data call on thesecond RAT; closing the first data call on the first RAT; and awaitingnotification of new data transmission destined for the multi-mode mobilecommunication device through the first active data connection over thefirst RAT.
 5. The method according to claim 1, further comprising:configuring a server of data transmission destined for the multi-modemobile communication device to use the first active data connectionwhile there is no data to be transmitted, and the second active dataconnection while there is data is to be transmitted.
 6. The methodaccording to claim 1, wherein the first criteria is selected from thegroup consisting of: a tariff; a call set-up latency; a data latency;data rate; reliability; a data throughput requirement; a concurrencywith other services; and a combination thereof.
 7. The method accordingto claim 1, wherein the second criteria is selected from the groupconsisting of: a data throughput requirement; a tariff; a call set-uplatency; data rate; reliability; a data packet latency; a data packetjitter; a concurrency with other services; and a combination thereof. 8.The method according to claim 1, wherein the first RAT is a cellularradio access technology, and the second RAT is a wireless local areanetwork radio access technology.
 9. The method according to claim 1,wherein the first RAT is a wireless local area network radio accesstechnology, and the second RAT is a cellular radio access technology.10. The method according to claim 1, wherein the first RAT is a firstcellular radio access technology, and the second RAT is a secondcellular radio access technology.
 11. The method according to claim 1,wherein the first RAT is a cellular radio access technology having afirst configuration, and the second RAT is the same cellular radioaccess technology having a second configuration.
 12. The methodaccording to claim 1, wherein the first RAT is a first wireless localarea network radio access technology, and the second RAT is a secondwireless local area network radio access technology.
 13. A methodcomprising: using a first data connection between a server and amulti-mode mobile communication device to detect a data transmissiondestined for the multi-mode communication device, said first dataconnection carried over a cellular radio access technology (RAT);detecting arrival of the data transmission through the first dataconnection over the cellular RAT; using a second data connection betweenthe server and the multi-mode mobile communication device for the datatransmission between the server and the multi-mode communication device,said second data connection carried over a wireless local area network(WLAN) RAT; determining a termination of the data transmission betweenthe server and the multi-mode communication device; and using the firstdata connection over the cellular RAT to detect other data transmissiondestined for the multi-mode communication device.
 14. A multi-modemobile communication device comprising: a first transceiver adapted tobe connected to a server using a first radio access technology (RAT); asecond transceiver adapted to be connected to the server using a secondRAT; and a processor for selecting a first data connection between aserver and a multi-mode mobile communication device while there is nodata to be transmitted, said first data connection carried over a firstnetwork utilizing a first RAT based on a first criteria, and selecting asecond data connection between the server and the multi-mode mobilecommunication device while data is being transmitted, said second dataconnection carried over a second network utilizing a second RAT based ona second criteria.
 15. A multi-mode mobile communication devicecomprising: a first transceiver adapted to be connected to a serverusing a first radio access technology (RAT); a second transceiveradapted to be connected to the server using a second RAT; and aprocessor for using a first data connection between a server and amulti-mode mobile communication device to detect a data transmissiondestined for the multi-mode communication device, said first dataconnection carried over a network utilizing a cellular RAT, detectingarrival of the data transmission through the first data connection overthe cellular RAT, using a second data connection between the server andthe multi-mode mobile communication device for the data transmissionbetween the server and the multi-mode communication device, said seconddata connection carried over a network utilizing a wireless local areanetwork (WLAN) RAT, determining a termination of the data transmissionbetween the server and the multi-mode communication device, and usingthe first data connection over the cellular RAT to detect other datatransmission destined for the multi-mode communication device.